Wilwood offers a compact aluminum master cylinder specifically engineered for the manual brakes on
C2 Corvettes. Not only is this an all-new, lightweight unit, but the bore is sized to make the brakes more effective with less pedal effort.
Part number 260-16521, with a 15/16" bore, improves line pressure by more than 10% for a given amount of pedal force compared to the stock 1" bore. For a further reduction in pedal effort or increase in caliper clamping force,
part number 260-16520 has a 7/8" bore.
Below from VanSteel
"C2/C3 Wilwood Master Cylinders
The hydraulic side of the brake system is based on leverage ratios. The overall system leverage ratio is a function of:
1. Brake pedal ratio
2. Master cylinder bore size
3. Effective caliper piston area
An OE manual brake C2 or C3 by my comparison formula has a 36:1 front circuit leverage ratio. The rear circuit is a little over 19:1. When you compare those two leverage ratios front to rear, that gives you your static front to rear bias ratio which in this case is 65/35.
If you use the 1.125″ MC on a manual brake D8 caliper car, instead of the normal 1″, your front leverage drops to 28.5:1. When you drop to the piston area of his SL6 calipers, and using the 1.125″ power brake master cylinder, your front leverage ratio drops to 21:1, representing a 39% loss in brake leverage from OE D8. That translates to requiring 39% more leg effort to get comparable clamping force.
So yes, it will make a measurable difference.
And for an FYI, the current version of the SL6 using 1.75/1.25/1.25 pistons with a 15/16″ bore master cylinder give a front circuit leverage ratio of 36.19:1 which is a hair higher than OE D8 manual, but probably not enough to feel a difference.
If you install the 7/8″ master cylinder, this will restore the front leverage ratio to 34.7:1, or almost back to to OE D8 effort levels. The pedal will be slightly firmer than an OE D8 manual brake car, but will now be able to make 39% more pressure with the same amount of pedal effort."